Haefulz said:
Back on the topic of evolution: Another common criticism of natural selection is the development of more complex body parts such as an eye. Some say species couldn't have developed eyes through evolution because without the entirety of the eye (iris, pupil, retina, etc.), the eye as a whole would be useless, so species that developed mutations with only one part of the eye wouldn't survive, thus wouldn't reproduce. In my opinion, this is one of the best counters to natural selection, though I've seen some answers for it that haven't quite satisfied me.
I understand the confusion but first you need to accept a few things:
1) just because something isn't useful at first, doesn't mean it gets selected out of the gene pool. For example: a multi cellular organism mutates by chance (and it is always by chance) in its DNA. It now has a couple of cells somewhere in its body that can detect green light. Is it useful? Not yet probably. But is it harmful? Nope. So if this organism has other characteristics so that it survives and reproduces, light detection gets introduced into the gene pool. It is still a long way go to an actual eye. But the road is not inconceivable. What if in a 1000 years (or more) another mutation occurs that transfers all these cells to the surface of the organism. This organism can now detect light. If this organism discovers that there are more predators when there is light (because it is warmer then? I'm just giving an example here) he can adapt to hunting for food at night. This gives him a MAJOR advantage. You would probably say that he needs a nervous system and a brain for that but not really. Maybe out of ten organisms that can detect light, there is one that doesn't like light. He will stay away from it. The other nine will have a higher chance of getting eaten. The one will most likely survive. This is just one example of how this could work.
Another 1000 years and red and blue get thrown in their. He can now see the spectrum as we can see it. Etc etc... After a million years you have the rudimentary eye ball.
2) in a park close to my home there lived an albino pigeon. It was the only albino pigeon there. Random mutation bla bla bla he had no pigment. Now. He lived on and even built a nest with his partner. So he didn't get selected away by predators or not finding a mate. You know what happened to him? He was in his nest guarding his eggs when lightning hit the tree. That's just plain old dumb luck. And I doubt that being albino made him more attractive to lightning. Sometimes random mutations that have no advantage/disadvantage have some bad F'ing luck.
Evolution in its simplest way of looking at it is like this:
A) random mutation occurs. The mutation gets tested for advantages/disadvantages in the current environment
A.1 it gives the organism a disadvantage: he (probably) dies off.
A.2 no advantage/disadvantage yet: it (probably) stays in the gene pool
A.3 it gives the organism an advantage: it is (most likely) accepted in the gene pool
A.4 the organism gets hit by lightning or something: tough luck
PS: sometimes evolution is weird. Humans don't really use their appendix any more so why doesn't it go away? Because when the appendix becomes smaller it has a higher chance of infecting (aka killing the person). So we now have an appendix that isn't used but it doesn't go away because that would kill us. Weird huh.
B) the environment changes somehow (I'm using the butterfly example)
In England during the industrial age, pollution changed white trees into black trees (cuz of all the dust). White butterflies normally lived on these trees so predators couldn't see them. Now that the trees were black, the butterflies were easy pickings for the predators. But some butterflies had a darker pigment so were harder to spot.
They survived because of a mutation that was disadvantageous just a couple years before. How the tides can change
. So now in a few generations time, the butterflies change from white to black.
There is more to it but that is the most important part. What you should remember the most is the difference between A.1/2/3/4.
